Steam generator



Jan. 2, 1951 B. N. MCDONALD 2,536,072

STEAM GENERATOR Filed July 5, 1947 56 f; g. l

f oooooouoooooco o 0 O 0 0 0 0 0 O 0 0 00000000000000 0000000000000 0 O0 D 0 O 0 I00 0 0 0 0 00000000000000 00000000000000 0 0 O 0 U 0 O O O O0 0 0 O 0 0 O O 0 00000000000000 0 0 0 O 0 0 a D 0 0 0 00000000000000138 w I H 'flll llillllll L Iii F1 ID 1 5%;? INVENTOR ATTORN EY PatentedJan. 2, 195i 7 STEAM GENERATOR Bertrand N. McDonald, Aurora, 111.,assignor to The Babcock & Wilcox Company, Rockleigh, N. .L, acorporation of New Jersey Application July 3, 1947, Serial No. 758,755

Claims.

This invention relates to steam generators, and it involves theparticular construction and arrangement of a convection superheater, fora steam generator.

. The invention more particularly relates to a steam superheaterconsisting of a bank of spaced fluid heating tubes, the bank of tubesbeing formed by return bend connected platens with the successivetubular sections of each platen connected at their ends for series flowof fluid therethrough from a single inlet of the platen to its outlet.

The invention also involves a steam superheater in which the successiveplatens are arranged structurally in parallel and with their planestransversely related to the longitudinal axis of an inlet header fromwhich the platens receive fluid to be heated. Specifically, oneembodiment of the invention involves a superheater of the abovedescribed type, in which successive platens of tubes (lengthwise of theinlet header, or transversely of the gas pass) are interconnected inseries by pairs, at the top. Thus there is a continuous fluid flowthrough two connected platens, providing two fluid passes through astream of heating fluid, i. e., a gas stream.

An object of the invention is to decrease metal temperatures, for thesame fluid temperature outside the tubes and the same final fluidtemperature inside the tubes of the platens. This is of primaryimportance in steam superheaters where gastemperatures and steamtemperatures have reached such high values that, in many cases,expensive high alloy steels have been deemed necessary. The presentinvention provides for the use of much less expensive carbon steel tubesin installations which, without the invention, would require steel tubesof high alloy content and higher price.

Another object of the invention is to increase the overall rate of heattransfer so that less heating surface is required than would be the casewith-a conventional heater (or superheater) for the same steam and gasconditions.

Another object of the invention is to provide a fluid heater in. whichthe number of tube holes in theheader is materially reduced, thusaffording a substantial reduction in the cost of manufacture. vantage ofincreasing the header ligament efficiency, thereby permitting, in manycases, the use of headers having thinner walls.

The invention will be described with reference to the accompanyingdrawing in which a preferred embodiment is shown.

This also results in the additional ad- In the drawings:

Fig. 1 is a vertical section of a steam generator including theinvention;

Fig. 2 is a diagrammatic view in the nature of a plan section,illustrating the manner in which adjacent superheater platens areinterconnected in the superheater indicated generally at ID in Fig. 1.

Fig. 3 is a detailed view showing connections employed betweensuccessive upright loops of the superheater tubes; and

Fig. 4 is a transverse section on the line 4-4 of Fig. 3.

The illustrative superheater consists of a bank of series flow connectedtubular sections which are disposed in upright positions in the path offurnace gases proceeding from the furnace 12. These sections areconnected at their ends to provide such interconnected platens as thoseshown at A and B in Fig. 2, the outlet tubular section 36 of platen Abeing connected to the inlet tubular section it of platen B to afford acontinuous steam flow from the superheater inlet header l8 to the outletheader 20. The inlet header 18 receives its steam from the rear drum 2?.of a four drum bent tube steam generator which will be later referredto.

It is to be understood that Fig. 2 is representative of a small sectionof the superheater and that there are successive arrangements ofsuperheater platens similar to the arrangement of the platens A and B.One such successive arrangement is shown between the platens A and Beach with 6 tubular sections, however a platen may consist of only 2sections.

The steam flow from the superheater inlet header it through thesuccessive tubular sections 3i3fi of platen A is indicated by the arrow40. From the tubular section 36 the steam flows through a tubularcrossover connection 42 to the tubular section 46 and thence in thedirection of the arrow 46' through the successive tubular sections 41-52to the superheater outlet header 28. The crossover connection 42 isfurther shown in Fig. l as being disposed mainly above the bank of thesuperheater tubes.

The immediate result of the use of this arrangement of tubes is todouble the velocity of the steam flowing through the tubes, as comparedwith a conventional arrangement of platens in which all of the steamflows through the platens in parallel from the inlet header to theoutlet header. This increase in velocity has two major results. First,the overall rate of heat transfer is increased so that less heatingsurface is required than would be the case with the con-s,

assaova ventional superheater arrangement of platens, for the same steamand gas conditions. Secondly, for the same gas temperature outside thetubes, and the same steam temperature inside the tubes, the increasedsteam velocity results in an appreciable lower metal temperature. Thisresults from an increase in the conductance of the steam film on theinside of each tube, or tubular section, consequently decreasing thetemperature differential between the steam and the metal. This reductionin metal temperature permits the use of relatively inexpensive carbonsteel superheater tubes in place of expensive alloy steel tubes, in manyinstallations. The invention also results in a substantial reduction inthe number of tube holes to be drilled in the superheater headers andthis reduces the cost of the superheater construction. It also resultsin the additional advantage of increasing the header ligamentefliciency, permitting in many cases, the use of headers with thinnerwalls.

The invention, with its interconnected adjacent superheater platens alsoresults in a marked improvement in steam distribution, and this in turn,results in a lower maximum tube temperature, and longer tube life.

Now, referring to the steam generator as indicated in Fig. 1, thefurnace I2 is fired by a chain grate stoker Iii) from which the gasespass upwardly over a first bank of steam generating tubes ISL-65directly connecting the submerged drum 66 with the front steam and waterdrum 68.

After passing over the front bank of steam generating tubes the gasespass over the superheater which is supported mainly from the inlet andoutlet headers I8 and 28. These headers are supported in the mannerindicated in the drawings from a beam such as ill. At the bottom of thesuperheater its rear tubular sections such as 36 are supported by aclevis arrangement ineluding a connecting link it from the front tubes'54 of the middle bank of steam generating tubes 55. To maintain thesuccessive loops of the superheater platens in their operative positionssuch loops l8 and 89 are connected by clevis devices such as that shownat St. A similar clevis device 86 is shown connecting the loops 85 and88.

To maintain optimum uniform gas flow between the superheater tubesections such as those indicated at 3I-36 and 65I in Fig. 2, connectingstructures such as those indicated at tilt-2G2 are employed in the upperportion of the bank of superheater tubes. nections is indicated indetail in Figs. 3 and 4. They are shown between the tubes of the firsttwo transverse rows of the superheater, including such tubes as 3!, 32,46 and il'. Each of the tubes Si or is connected to the tube immediatelyin the rear thereof by the specific construction indi ated in Figs. 3and i. This includes in each instance bracket welded to the forwardtubes such as El, this bracket being provided with an opening throughwhich extends a U-shaped element 236, the legs of which are welded tothe rearward tubes such as The brackets 28% are aligned horizontallytransversely of the superheater on the tubes M or 5-6 and are providedwith recesses for receiving a transverse aligning bar 2528 which islocked in position against upward displacement by extensions 2H3 on theupper parts of brackets 28%. The bar 2138 is slidable into operativeposition from one side of the bank of superheater tubes and is One ofthese conadapted to maintain the superheater tubes in their operativealignment, preventing shifting of the tubes downwardly or upwardlyrelative to each other. Thus, the clevis constructions such as shown inFigs. 3 and 4 together with those such as shown at I2, 34, and 86maintain the integrity of the superheater as a separate bank of tubesand as a rigid unit supported from the headers I3 and 2t and from theforward tubes M of the middle bank of steam generating tubes.

The middle bank of steam generating tubes I6 directly connects the drum9Q to the submerged drum 3% and the furnace gases are caused to passdownwardly along the tubes of this bank by the construction andarrangement of baffles 92 and M. Toward the lower end of the middle bankof steam generating tubes 16 the gases'are turned as indicated by thearrow and proceed upwardly over the rear bank of steam generator tubesI39 and thence to the gas inlet of the economizer I522. The first threerows I04, I66 and I08 of the tubes of the rear bank I98 directly connectthe middle steam and water drum 96 with the submerged drum 3% while theremainder of the tubes of the rear bank directly connect the rear bankwith the submerged drum 56.

The front wall E it of the installation is defined by furnace steamgenerating tubes II2 connecting the header E It to the front steam andwater drum 3, the header H4 being connected for circulatory purposes,with the submerged drum by the circulators H6 and. H8.

Other steam generating surfaces are provided by the furnace side walltubes such as I20. These tubes, in Fig. l, are shown as connecting thelower head I22 to the upper header I24, the latter being connected bytubes such as I 26 to a steam and water drum. The lower header I22 isconnected to the submerged drum 56 by circulators such as I30 and I32.

Toward the rear of the furnace additional steam generating surface isprovided by the furnace Wall arch tubes I34 which directly connect thedrum 56 with the header I38 in the manner indicated in the drawing. Theheader I36 is also directly connected to the submerged drum 66 by thecirculators I38.

Rearwardly of the arch tubes I34 is a stratum Hill of heat resistingmaterial and a stratum [42 or" thermal installation. Similar materialsare provided for the front wall I50, the rear bafile I52, the rear WallI54 and the roof I56, encasing the pressure parts of the installation.The roof I5; is mainly supported by the circulators 56B and thesuperheater inlet tubes I62.

The circulators It!) extend from the steam space of the front steam andwater drum 68 to the steam space of the rear drum 22. This space isconnected to the superheater inlet header I8 of the tubes 5E2.Associated rows of circulating tubes such as Hit-N8, connect the samespaces of the drums 22 and 9E! and the drums 9i] and 68 are similarlyconnected by circulators such as Iii! and I12.

What is claimed is:

1. In a steam generating installation, horizontally spaced upright steamgenerating tubes, at convection superheater including a plurality ofupright parallel platens of return bend tubes connected for the seriesflow of steam through successive tubes, said platens constituting a bankof spaced upright superheater tubes disposed rearwardly of the steamgenerating tubes and transversely of the path of furnace gas flow, inletand outlet headers above said bank of superheater tubes, tubularcrossover means interconnecting adjacent platens to form groups with theoutlet tube of a first platen at the rearward part of the superheaterconnected to the inlet tube of a successive platen of the same group,said inlet tube being disposed at the forward part of the superheater,means including upright tubular extensions connecting the inlet tube ofthe first laten of each group of platens to the inlet header as a commonsource of steam, means including tubular outlet extensions connectingthe outlet tube of each group of platens to the outlet header, and meanstying together the return bend tubes and the platens of the superheaterso that the superheater is supported by the inlet and outlet extensions.

2. A convection superheater including a plurality of upright platens ofreturn bend tubes connected for the series flow of steam throughsuccessive tubes, said platens constituting a bank of horizontallyspaced upright superheater tubes disposed transversely of the path offurnace gas flow, inlet and outlet headers above said bank ofsuperheater tubes, tubular crossover means interconnecting adjacentplatens to form groups with the outlet tube of a first platen at therearward part of the superheater connected thereby to the inlet tube ofa successive platen of the same group, said inlet tube being disposed atthe forward part of the superheater, means including upright tubularextensions connecting the inlet tube of the first platen of each groupof platens to the inlet header as a common source of steam, meansincluding tubular outlet extensions connecting the outlet of each groupof platens to the outlet header, said inlet and outlet extensionsdepending from and secured to the respective headers and means tyingtogether the return bend tubes and the platens of the super-heater sothat the superheater is supported by the inlet and outlet extensions,said tying means including an aligning bar extending transverselythrough the platens of a plurality of groups and through bracketssecured to the tubular components of the platens.

3. In a fluid heating installation, a bank of horizontally spacedupright tubes disposed transversely of the path of furnace gas flow andineluding a plurality of parallel upright platens each formed of returnbend tubes connected for the series flow of fluid through successivetubes, tubular crossover means connecting the outlet tube at therearward part of a first platen of each group with the inlet tube at theforward part of a successive platen of the same group, means includingupright tubular extensions each connecting the inlet tube of the firstplaten of a group of platens to a common source of fluid, meansincluding tubular outlet extensions each connecting the outlet tube of agroup of platens to a common fluid outlet, said inlet and outletextensions being supported at their upper ends, means tying together thereturn bend tubes and the platens of the bank so that the bank issupported by the inlet and outlet extensions.

4. In a convection fluid heater including a plurality of horizontallyspaced upright platens of parallel tube lengths connected by returnbends for the series flow of fluid through successive 5 tube lengths ineach platen, said platens constituting a bank of horizontally spacedupright tubes disposed transversely of the flow of a heating fluid,tubular crossovers each interconnecting adjacent platens to form a groupof platens with the outlet tube length of a first platen near one sideof the heater connected to the inlet tube length of a successive platenof each group, the outlet tube length being disposed near the side ofthe heater opposite the side near which the inlet tube length isdisposed, the platens of each group being disposed in parallelism, andmeans tying together the adjacent return bend tubes and the adjacentplatens of the heater so that the heater is supported by the inlet andoutlet tube lengths, the inlet tube length of the first platen of eachgroup of platens being connected to a common source of fluid to beheated and the outlet tube length of each group of platens beingconnected to a common fluid outlet.

5. In a convection fluid heater including a plurality of horizontallyspaced upright platens of parallel tube lengths connected by returnbends for the series flow of fluid through successive tube lengths ineach platen, said platens constituting a bank of horizontally spacedupright tubes disposed transversely of the path of furnace gas flow,tubular crossovers each interconnecting adjacent platens to form a groupof platens with the outlet tube length of a first platen near the frontof the heater connected to the inlet tube length of a successive platenof each group, the connected outlet tube length being disposed near therear of the heater, the inlet tube length of the first platen of eachgroup of platens being connected to a common source of fluid to beheated and the outlet tube length of each group of platens beingconnected to a common fluid outlet, and means tying together theadjacent return bend tubes and the adjacent platens of the heater sothat the heater is supported by the inlet and outlet tube lengths, saidlast named means including an aligning bar extending transverselythrough a multiplicity of platens and through brackets secured to thetubular components of the platens.

BERTRAND N. MCDONALD.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,746,158 Loifler Feb. 4, 19301,883,707 Gordon Oct. 181, 1932 2,114,224 Jacobus Apr. 12, 19382,254,373 Langvand Sept. 2, 1941

